All this talk about filling huge cavities with wood blocks, epoxy and what not is crazy.
A new top would be a good alternative but will all of the effort involved, you might as well just start a new body. It will be quicker and better in the long run.
If that guitar were mine, I would leave the routes alone, re-paint, make a really nice pearloid pickguard for it and upgrade the bridge (Floyd or wilkinson). The biggest change I would potentially do is a two humbucker route - think Dave Murray of Iron Maiden.